Filter for purifying air



Dec. so, 1924. 1,521,575

H. WITTEMEIER FILTER FOR PURIFYING AIR Filed Jan. 5, 1921 5,sheets-sheet 1 ec. w, 1924. l 1,521,575

H. wTTEMr-:IER

FILTER FOR PURIFYING AIR i Filed Jan. 5, 1921 5 sheets-sheet? Jn venor v www Dec. 30, 1924.

H. WITTEMEIER FILTER PQR PURIFYING AIR 1921 5 sheets-sheet :s

Filed Jan. 5

BY (VWM Dec. 30,1924. 1,521,575

H. WITTEMIER FILTER Fon PURIFYING AIR Fileid Jan. 5, 1921 5 Sheets-Sheet 4 )4 j Fig. 13.

@wf/P@ Patented Dec. 30, 1924.

UNITED STATES PATENT OFFICE.

HANS WITTEMEIER," oF BERLIN, GERMANY.

FILTER FOR PURIFY'ING AIR.

Application filed January 5, 1921. Serial No. 435,288.

To alf whom/t may concern.' e

Be it known that I, HANS WITTEMEmm a citizen of Germany, and a resident of Berlin, Germany, have invented certain new and useful Improvements in Filters for Purifying Air, of'fuwhich the` followingfis a specification.

In many technical processes and plants the purification vof the air plays an 1m,

portant part. In heating and Ventilating plants the cleaning of the air is? necessary for hygienic reasons; in turbo-generators, compressors and the like the air must be deprived of' dust in order to secure theirI smallerI measure, finely distributed liquids."

'Hitherto the preference hasgenerally been given to fibrous stuffs in the form of filtering cloths. But these still hays' two serious drawbacks. In the first place, the clogging up of the .cloth by the "dust results in a rapid increase of' the resistance offered to the air passing through it; and secondly, even` if they are impregnated with a non-combustible agent they are not sufficiently proof against fires, which are liablev to occur, especially in electric generators.

This drawback had to be met by providing special fire-preventing flaps.

These drawbacks are o'bviatedby mak.

ing the filtering .members of layers of noncombusti-ble bodies of any geometrical shape such as balls, cylindrical or prismatic rods of glass, porcelain, etc., which, in order to increase their .adhesiveness, are coated by'a non-evaporating liquid such as glycerine or the like.

The advantages offered by thenew inven-j. tion are as follows: The proneness of the filter to become rapidly clogged with impurities is removed, becausethe dirt-removing opera-tion principally consists in repeatedly deflecting the innumerable air jets into which the whole air current is divided. The arrangement of the filter may be such that the untreated air first encounters al layer of comparatively large iballs and then palses through additional layers of finer ba s. i

Another advantage is that the casing of the filter' may be madeof any space-saving shape such a"s rectangular, round, etc.,

whilst it is known that cloth fil-ters are ,lim-- ited to rectangular shapes for technological reasons. I

Finally, special mention must bel made of the extraordinarily convenient manner inl which the various elements of the filter may be cleaned whilst the plant is in operation. The filter balls are simply taken out at the foot of each element of' the filter, and then washed and replaced through the top. Thus a simple mechanical cleaning process is em'- ployed and the soiled filter .material is always re-used after cleaning, Whilst the so-called filter cloths ha'd to be cleaned from time to time by a chemical process and were worn outvery much faster.

The invention is illustrated in the drawings in which-v e Fig. l is a front view of an element of a filter,

Fig. 2 is a horizont-al section of the same, Figs. '.3 and f show a special constructional form of a wall ofthe filter cells, and Fig. 5 shows-how the filter elements are united into bays.

Fig. '6 isa perspective view of one of` the cells and its frame shown as removed from the supporting frame of Fig. 5.

Fig. `7 is a section on line 7-7 of Fig. 5; Fig. 8 is a perspective viewy of other forms of filteringl members of `cylindrical formg,

Fig.' 9 is a perspective View of still another form, also of cylindrical contour;

'Fig 10 is a perspective' View of still ani other form of prismatic shape;

Fig. 11 is a diagrammatic view of'ther I action of air in respectcto several of the filter members;

Fig. 12 is also adiagrammatic view of same, but taken at right .angles to Fig. 11;

Fig. 13is a front view 'showing a plurality of filter cells in docket like'pockets; Fig. 14 -is a yertic'al: section y.taken on line -14-.14 of Figure 13, showing the filter elements or cells eaclrsarranged infga slant ing position wall; 4

Fig. 15 lis a front View, partly in section; Fig. 16 a horizontal.-section, and

in a separate aperture inthe desired shape and thrown in in any manner.

The bodies a are made of any suitable noncombustible material and moistened with glycerine or any other viscous liquid.

The balls a moistened with glycerine are stacked `up in the space between the wire grids b and cause the current of uncleaned air to be divided up into a large number of jets and to pass along tortuous paths. Inl passing along these paths the impurities, such as dust and dropsof water brush against and are retained by the surfaces of the balls. To enhance the seizing effect of the impurity-retaining balls, these latter may be provided with roughened or ribbed surfaces.

The air passes from the room c 'containing the uncleaned air through the front wall of the box or case and deposits its impurities on the retaining bodies b, and then passes out of the rear wall of the case into the cleaned air chamber.

In Fig. 1, eight cells are visible and in Fig. 2, twelve cells are visible.

At. the rear of the moistened retaining bodies another filtering layer may be arranged which is dry so as to act as a 'moisture-collecting agent that retains any particles of liquid that may have been carried along. This dry layer may be made similar to the dust catching layer, or any other material or bodies suitable for accomplishing the desired effect may be employed. Suitable substances are. for example, asbestos,-

glass wool, or the like.

In the preferred arrangement, the layer i. of dry filtering bodies is not placed 1minediately behind the moist layer, but an empty space is left between them. The a-ir which streams through the first layer at a comparatively high speed and deposits its dust in the first layer, but which is liable to carry fine particles of the moistening fluid along with it, become steadier in the empty space and shedsmost of its moisture in this space. Any remaining moisture is completely removed whilst the air is passing through the layer 'of dry filtering bodies.

If desired, the filter may even be provided with a dry layer formed of granules that are adapted to bind water, so that the air owing through the dry layer is not only deprived of any particles of water but also of the water contained in the air in a gasfilter wall, may be obtained by making the wall of perforated sheets whose `perforations are completely or partly covered at the side next to the filtering layer by small inclined surfaces or roofs that slope dowuward towards the said layer.

Perforated sheets of this kind can be made, for instance, by partially stamping small tongue-shaped surfaces out of' a, sheet and bending all the small tongues to one side, so that a wall is formed that is sonic what similar to the scaled surface of a fish. Dripping walls of this kind, i. e., 'walls from which the liquid drips off at one and the same side can also be made up of fiat iron strips arranged like a.Venetian hlinu with each strip inclined downward towards one side.

The desired result is accomplished in a very efficient mannerby means of trellislike sheet metal whose strip-like surfaces are all inclined downward towards the saluey side. A portion of a sheet of this kind is shown in Figs. 3 and 4. This is produced by making staggered slits in a sheet and then stretching it, when the illustrated trellis-like structure with slanting surface element-s will result. A liquid trickiingdown such a sheetof slitted stretched metal always tends to flow to the side towards which the various strips of the sheet slopey in a downward direction, so that the liquid is completely prevented from passing tlnfoir-h to the opposite side.

The liquid caused te trickle down :uri over the dust-retaining bodies and to um.. ten them may also be au alkaline liquid.

The said bodies may themselves consist of ble to produce filters of any desiredsize inv the shortest possible vtime from .parts th are kept in stock, because the individual panels can be put together in any desired manner according to the particular' purpose in view. The novel filters are much lighter, easier toZ re lace, and hence .more readily -repaired than known kinds.

A special method of constructing the individual filter panels and the individual filter cells attached thereto, as well as a spe? cial manner of arranging these panels and cells in openings'in a filter bay that is lbuilt into an opening in a wall, is shown in Figs. 13 and 14. The arrangement according to these figures is suchthat the filterl walls, between which the dust or moisture-retaining bodies are enclosed, do not extend vertically, i. e. at right angles to the direction of the hole or 'passage t-hroughir the wall in which the filter'is placed, but are' arranged in a slanting position. The current of air which passes through the wall is thus deflected by the air filter from its normal direction.

This arrangement offers manyadvantages. In the first place, the effective surface of the filter is very much greater than the cross-sectional area of the air channel or passage, which latter, in ordinary arrangements, is approximately equal to the area of the filter. Secondly, the novel arrangement renders it possible to so arrange the manner to a chest of drawers.

-filter cells and sliding frame are easily con-l filter cellsthat each individual cell may be conveniently taken out and replaced, thisbeing important for the cleaning and renewing of the dust-retaining coating of the dust-retaining bodies. The cells filled with ythe dust-retaining bodies are pushed into slideways Z2 in the filter bay' in a similar The slideways d2 are arranged to be perfectly dust tight so that no dust can pass through any art of the filter passage.

Another advantageous feature is that the 'structed of very simple elements yconsistingr of pieces of Asheet of uniform size, each of which is simply bent into the form of a. long angle bar. The .slidewayszj are also made by thus bending pieces of sheet metal of. ,uniform size.

' Fig. 13 isa frontview and Fig 14 is a ver-V" ticalsectioniof a filter bay of thls kind. ,In-v

serted between 4the sloping filter walls a2 are filtering bodies b. The yfilter cells are 'slipped into the docket-like openings c2 vof the bay, the lateral sliding bars at the top of the cells being adapted to slide in the lateral slideways d2 attached to the side walls of the openings o2. Handles et are provided by which the individual filter 'cells can easily be pulled out.y The bottom cell is` shown drawn half way out in Fig. 14. The

individual frames of the (bay are preferably screwed together by screws f2. 'The general' flow of the air is indicated by the; arrows shown in Figure 14. f l

In Figs. 15 16 and 17 a special kind of dust-retaining members or bodies is shown which is moistened with the aforesaid viscous liquid. The dust orl moisture-retaining bodies consist of vertical rods or bars arranged in staggered rows of a suflicient number for the purpose in view; 7 rows being i shown in the drawing, Fig. 16.'- Each bar is fixed by lu s e3, one at the bottom and 'oneG at the top, w ich fit into holes inthe bottom and top transverse bars d3 oflthe frame and are 4bent round after they are slipped through the said holes. The air -to be cleaned, on entering the filter, whichl may b e composed of any number of/cellsor panels, impinges upon the bars, which should be moistened, or have liquid continually trickling down them. By the time the air reaches the other side of the filter, it will be quite clean 'so that it leaves the filter in a pure0 estate and the flow of the air is indicated by the arrows 19, The curved bars c3 provide quiescent spaces leeward ofthe air flow passy ing in the direction of 'the arrows 19. 4The side walls b3 restrain the air How therebetween. The frames a3 may be securedto each other by bolts k3. The filter cells may be held to the walls b5 of the frames by bolts fj?. A handle f3 facilitates the removal of the cells. The'front of the cell is indicated by 20 and the rear by 21.-

From the foregoing, 1t will have been seen that the filter cells such as used in the structures .shown in Figs. 2, 6, 7, 14 andv 16, for

streaming through the depth 'of the group of members to calm the' air. `That is, the air. ,is rendered still or quiet and it 'is l free fronr that which `might cause motion. .f Within such spaces of becalmed air irregular tri- Aangular-like spaces or spandrels are 'formed example, are formediof'membe'rs which are in which the dust is arrested. The dust contacting with theviscous coatings lining the spiracles' gathers in the protected cdrners l -thereof, until the cell is cleaned as herein- A1 of the frame. cell shown in Fig. 2, in whichthe depth e of the part k of the frame A is less than the before described. In all of the embodiments shown in the drawings, the filtering material or bodies are relatively small, and provide a large surface. As an example, may be given one cubic foot of filter bodies equal to two hundred square feet of surface.

This invention may be developed within the scope of the following claims without departing from the essential features of the .-:ame and it is desired that the specification :1nd d ia\\'ings `be read as being merely illusrative and 'not in a limiting sense except as necessitated by the prior art. From the foregoing description and drawings, it is clear that the filter shown in Fig. 2 consists of a frame A, incombustible walls o, having openings therein, intermediary walls b, having openings therein, and incombustible filtering means a between the walls. The air v passes in the direction of the arrows. The

frame A hasy a relatively small depth A1, that is, the height A2 or width A3 of the frame is considerably greater than the depth This is also true of each height f or Width g. This frame h has an open front and an open rear, and across the front and rear the perforated or reticulated walls d and c of incombustible material are provided to complete the cell. Preferably ythis wall i at the front is like that shown in Figures 3 and 4, obtained by expanding metal whereby sharp corners mare formed. The rear wall .la of a cell of Fig. 2, may be of sieve-like material like that shown in Fig. 1. In Fig. 2,the entire front c is exposed freely to the atmosphere, that is, there are no channels, or conduits, or the like necessary, but the entire surface is open directly to the atmosphere, and in free communication therewith. It is the same with the rear wall c". Thus, the entire front and rear wall is in free communication with the atrvspaces in attenuated form, 'spreads out, since several streams from different direction meet or unite in the enlarged space and then from this union of air, individual streams again develop and pass through' in between the spheres in attenuated form. It may be .said that each outgoing individual stream has some part of the air of each incoming vindividual stream'that entered the uniting space. This repeats itself, and thereby suc- It will be noted that cessively the air divides and re-unites. f

Thereby the dust held in the air is separated from the air, and drops on the viscous coating of the filteringvmembers and is temporarily held thereby. the coatin is in the direct and general path of the air fiow, is moved along in the coating until it lodges and is arrested at a place where it is not influenced by the general air-flow. Such places are, so to say, leeward to the wind, or in partial or 'total eclipse to'it, in other words, ecliptic portions of the members arrest the dust separated from the air. Some of such places form protected pockets. These pockets are formed by contiguous walls of the members out of the path of the general air fioW. The coating accumulates more in the pockets than in the exposed surfaces of the members, and the dust settles in these accumulations of viscous maternal, namely, in such places where they are not under the influence ofthe general direction of the air-flow, and are thereby held in position until the filter is cleaned.

The repeated and successive sub-division and re-uniting of the air sets up what may be called a breathing, and this breathing of t-he cell, may be said to be in synchronism with the, vibrations of the atmosphere', so that as the air from the surrounding atmosphere enters the filter cell and is sub-divided and re-united, it deposits its dust in the interstic'esy between the filter bodies, and then leaves the filter cell in free-from-dust condition.`

The cleaning action may be said to be automatic, since no forced pressure is essential as in the prior art, nor any guiding means as conduits are required, and pumps are en- Such dust as falls on of the filtering members, which A tirely dispensed with. Slight differences of temperature between the front and rear of the filter are sufficient t-o bring about a passage of air therethrough. If a filter is placedv in a Wall of a-room which encloses a dynamo, with the exterior of the filter exposed to the exterior atmosphere, the comparatively slight agitation vor suction of the air produced by a dynamo in its room is sufficient to cause a passage of air through the filter in the wall.

Tnstead of the spherically shaped filtering members as shown in Figure 2, cylindrically shaped members a4, ai", and.. ai, as shown in Figs. 8 and 9, may be used or also prismatically shaped members a7, as shown in Fig. `10, or any other shape may be used. My invention does not resi placed regularly or irregularly in respect to each other.

In Figures 11 and 12, there is shown diagrammatlcally the eneral activity of the air as it passes by t ev spherical bodies for e in the shape of such bodies .per Seybut in the aggregatev action thereof, and such bodies may be instance, but the action is substantially the same with such other bodies as hereinbefore referred to: The air flows through the more or lessnarrow interstices `between the filtering bodies a in more or less attenuated streams s until it reaches a larger space u where there is a union of the various. streams s. Then this again separates mto streams 't which streams consist of some air from each I When deposited on the coating which is in of the streams s. The union of the various streams in the uniting space in a diffusing manner, cause the dust to separate from the air and deposit"y onV the viscous coating.

the path of the general air flow as those in'- dicated by y they move along until protect- 4ed b'y the pockets p, where they permanently deposit inthe oil aggregate z. In Figure 11, the general air How is shown by the arrow 71 and the diffusing characteristic by the dotted lines j. It is not intended to have arrow indicate a forced current which would draw with it the dust, insteadof allowing it 'to deposit.

In Fig. 5, the interchangeable-units a', are supported by an auxiliary frame, which is U-shaped in cross-section as show in Fig.

7, and which is self vsupporting and in turn 'supports the filter units when held by the joining means.

' Theabve prlnciple underlying the'operation of the filter has been described in order to 4make clear the principle of operation underlying the invention, but further and I more specific theories based on known scientific principles relating-to air, eddy currents, diffusion, etc. will be clear to vone skllled 1n this art.

' I claim:

1. A self contained 'air'ilten'comprising' bustible` filtering means between the walls,

arranged to repeatingly and successively subdivide the air entering through one wall,

utosmall attenuated streams and reunite lthe same and again sub-divide the same" other wall free from dust.

between the'walls, and a viscous coating for the ltering means whereby the dust is collected by the same on the filtering means between the walls, the air leaving the other wall free from dust. Y

2. A self contained air filter, comprising.

a frame, incombustible walls for they open `{1i-ont and rear 'bf said frame, having air munication therewith, the wa' passage openings therein, the entire front and'rear walls adaptedto be exposed to the atnrosphere sol as to be in free and o en combeing spaced apart a distance less than either the length or the breadth of the walls, incombustiblel ilterin means of geometrical shape between t e walls, arranged to lrepeatingly and lsucxcessively subdivide the air entering through one wall, into small attenuated streams and re-uniting the same and `again sub-dividing the same between the walls, and a viscous coating for the {iltering means whereby7 the dust is collected by the samepn the filtering means between vand rear walls adapted to be exposed to theV latmosphere so as to be in free and open communication therewith, the walls being y spaced apart a distance less than either the length or the breadth of the walls, incombustib'le filtering means between the walls, arranged to repeatingly and successively subdivide the air entering through one wall, into small attenuated streams and reunite the same and again sub-divide the same between the walls, pockets out of the path of the airflow protected by the filtering means, and a viscous coating for the filtering means within the pockets whereby the dust is collected by the same on the filtering -means between the walls and within the pockets, the air leaving the other wall free from dust.

4. An air filter, comprising a frame, in combustible walls for the open front and rear of ysaid frame, having air passage openings therein, the entire front andrear walls p adapted to be exposed tothe atmosphere so as to be in free communication therewith, the walls being spaced apart a distance less than either the length or the breadth of the walls, and the front wall having sharp edges/'fl inthe path of the incoming air, in'combusL tible ltering means between the walls; arranged to repeatingly and successively subdivide the air entering through one wall, into abruptly formed small attenuated streams and re-unite the same into larger streams between the walls, and a viscous coating for" the filtering means whereby the dust is collected by the same on the filtering means between the walls, the air leaving the 5. In combination, with a plurality7 of interchangeable. units, each consisting of a frame, incombustible walls spaced apart for said frame and'having air passages therein, an ,incombustible filtering means between the walls having a viscous coating thereon and forming .air passagesfof restricted and expanded configuration# and incombustible auxiliary interchangeable frames each surrounding one of the filter. unit frames for holding the same, and means Ajoining the lined air-holes therebetween, the depth of' the group being\ less "than the length or breadth thereof, andan enclosing frame along the length' and breadth thereof, the barricadedspaces of the air-holes in respect to the air moving through said depth, calming the air, and the sheltered portions of the air-holes arresting the separated dust therein.

7. In combination with a plurality of interchangeable lilter units, a main frame, and a plurality of auxiliary interchangeable frames each surrounding at least one of the filter units for holding the same, said auxiliaryl frames adapted to bear one upon the otherin superposed and laterally adjacent -in superposed and laterally operative contact, one with the other, the auxiliary frames being self-supporting.

In testimony whereof he hereby aflixfes his signature in presence of two witnesses. HANS WITTEMEIER. Witnesses E. H. LORD, ARTHUR Sonnonn'nn. 

